Thursday, January 01, 2009

Chicxulub crater

The Chicxulub Crater is an ancient impact crater buried underneath the Yucatán Peninsula in Mexico.Its center is located near the town of Chicxulub, after which the crater is named—as well as the rough translation of the Mayan name, "the tail of the devil."The crater is more than 180 kilometers (110 mi) in diameter, making the feature one of the largest confirmed impact structures in the world; the impacting bolide that formed the crater was at least 10 km (6 mi) in diameter.

The crater was discovered by Glen Penfield, a geophysicist who had been working in the Yucatán while looking for oil during the late 1970s. Evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas. The age of the rocks and isotope analysis show that this impact structure dates from the end of the Cretaceous Period, roughly 65 million years ago. The impact associated with the crater is implicated in causing the extinction of the dinosaurs as suggested by the K–T boundary, although some critics argue that the impact was not the sole reasonand others debate whether there was a single impact or whether the Chicxulub impactor was one of several that may have struck the Earth at around the same time. Recent evidence suggests that the impactor may have been a piece of a much larger asteroid that broke up in a collision in distant space more than 160 million years ago.